This large atrial septal defect with left-to-right shunt resulted in pulmonary hypertension with increased pulmonary arterial pressures that eventually led to reversal and right-to-left shunt, resulting in marked right ventricular hypertrophy. This result from a cardiac septal defect is known as Eisenmenger's complex. The finger at the left is holding a markedly thickened right ventricular free wall below the tricuspid valve, and the finger at the right is holding the interventricular septum.